The Nine Cylinder Saab Steam Engine

Posted on 04. Apr, 2008 by in 2000-2009, Innovations


Photo Credit: Saab-Scania AB

In 1974, Saab-Scania Sweden’s Saab Car Division began developing what is known as the “Saab Nine Cylinder Axial Steam Engine” also known as project ULF.

This 250-hp nine cylinder steam engine was quite small, but it packed a punch while requiring a boiler and a large condenser with a buffer tank. The best part about this engine was that it required minimal fossil fuels and included miniscule carbon emissions.

At the time, Saab believed that they had overcome the most difficult obstacles with this engine that included everything from freezing, lubrication, cooling and starting time.

The steam generator itself operated at a working pressure of 100 bar at a temp of 662 degrees fahrenheit. This generator consists of 120 parallel tubes, spirally wound and brazed together. The tube’s internal diameter is only one mm.

The main expander included nine cylinders arranged axially in a ring around the verticle shaft, with a swashplate drive to the fina-drive unit and differential integrated with the crankcase. It is a uni-flow type with a variable cut-off control. This unit was geared to run at 3000 rpm at 90 miles per hour. The exhaust temperature from this engine was lower than one would expect at 180 degrees to a maximum of 482 degrees fahrenheit.

There was a liquid fuel burner that warmed up the water boiler that poured into the main expander engine. so there was a slight use of fossil fuels.

This quiet engine was designed and operated to drive the front wheels directly just like a conventional engine of its time and many to this very day.

It is notable that at the time, the Environmental Protection Agency in the United States awarded Saab-Scania AB for this successful steam engine development at the same time they were sending funds directly into stateside research steam-baed projects that never went as far as this project did.

According to a number of the research articles in this source, Saab-Scania AB’s Saab Car Division not only planned to continue this project well into the 1980’s, but they also planned to apply this nearly completed project to all of their production cars in the future.

So here is the question, what happened to this innovative breakthrough from Saab? It would appear that a project like this that was apparently shelved, should be reinstated, updated and included in Saab’s research and development today for alternative energy sources such as their ongoing BioPower and Hybrid programs. It would seem logical that the idea of using water to create steam is not a new idea and that it would be probably a less expensive and simpler solution than all of the existing alternatives being developed today.

Source: The Printed Word For ’74 – Saab-Scania of America, Inc.

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25 Responses to “The Nine Cylinder Saab Steam Engine”

  1. Drew

    04. Apr, 2008

    Very cool! I love all the stuff you find and write about.

    Reply to this comment
  2. Erich Haun

    04. Apr, 2008


    Reply to this comment
  3. iamchris

    04. Apr, 2008

    Cool story, thanks for sharing!

    Reply to this comment
  4. saab96

    04. Apr, 2008

    ” it required no fossil fuels and included zero emissions carbon emissions.”

    So what was the power source??

    Reply to this comment
  5. brent

    13. Dec, 2009

    BMW makes a latent heat battery to warm the engine in the morning. This battery could also be used to pre warm the boiler water.

    Reply to this comment
  6. Ryan

    13. Dec, 2009


    Hello. That’s a great idea, then no petroleum products would ever need to be used!

    Would the battery be charged as a plug-in?


    Reply to this comment
  7. Ryan

    13. Dec, 2009


    Hello. That could be a better way to ensure no petroleum products are used at all.

    Good thinking.


    Reply to this comment
  8. will

    29. Jul, 2010

    um…did you read the article? the battery that brent is refering to is just for PRE warming the water. This would mean less time to get going, especially if the water were below 40 degrees F. ..although I am not missing your sarcasm ryan, any ediot should know we get our electricity from fossil fuel (mainly)…some places have hydro and wind power as well. Yes, there would be fossil fuel type emissions, in order to create pressure with STEAM one must create steam. How does one get steam…?…heating water with another fuel source. This is where carbon emissions will happen, but according to the article only minimal amounts of fossil fuels are needed…as for the main exhaust, steam is the biproduct. as we all should know steam is just water vapor.

    Reply to this comment
  9. alessio215

    28. Dec, 2011

    we are still with thraditional otto engines thanks to the Americans.
    If the americans didn’t stick the nose in everything.
    we would be 40 years ahead of now

    Reply to this comment
    • Biged

      29. Jan, 2020

      Without the Americans “sticking their nose in everything” you would most likely be driving a skate board with wooden wheels!

      Reply to this comment
  10. Sam

    01. May, 2013

    Steam engines actually require a fair amount of fuel. In a typical steam engine (and the SAAB unit qualifies as typical) oils are burned in a steam generator (boiler) and most of the heat is transferred to the steam which, upon entering the cylinders or turbine expands, transferring some energy to the drive shaft. The expanded steam flows to t condenser, where it throws away the remaining heat. The advantage of steam is that oils such as gasoline are better at heating tubes than they are at exploding inside an engine, so you make a bit more use chemical energy. A significant advantage is that steam engines have so much torque that they can drive wheels more directly than ICEs (which naturally require transmissions to match engine speed to road speed). It’s also easy to reduce heat losses with extra plumbing and insulation, improving fuel economy further. Theoretical fuel economy is great with steam, but not magical, and steam cars would have vastly different maintenance needs. I prefer them in concept to ICEs, but I understand how they work and why we don’t see them on the road.

    Reply to this comment
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    01. Jan, 2014

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  16. Ivan Samec

    15. Jan, 2019

    When article is missing somethinh cardinal, it is clear that it is Achilles heel.

    So query is: What CoE has this nice engineering exhibition?

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  17. Butch Rogers

    16. Jan, 2019

    What heated the water to make steam?
    Why was this type engine never installed in cars?

    Reply to this comment
  18. Paul SHUBSACHS

    16. Oct, 2019

    Fascinating; but doomed to failure! Swashplates, Uni-flow, and nine cylinders, all crazy. Three cylinders, conventional crankshaft, and “double-beat” valving would have held more promise.

    Reply to this comment
  19. peter platell

    30. Mar, 2020

    Hallo Everybody , My father was the project leader for Saabs steam engine project. We have worked o and off with the technology with universities and industry when some people get excited about the potential but it is not until now real interest has set off. The unique capability to exploit a wide range of energy sources and high specific power ( kW/kg, kW/USD) makes it interesting for many stationary applications but also automotive applications
    PS we don’t use swash plate , we use wobble plate and we think the multi cylinder axial engine offer many advantages as a modern high tech steam engine

    Reply to this comment
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